I posted a few weeks ago about my Phantom starting to shiver like it was cold when you first take off. That problem got a bit worse yesterday (Jan, 26). While flying in a confined area it was quite challenging to control the position of the craft. I had good GPS lock. I could fly it but the craft just didn't fly right. When flying straight in GPS mode it would suddenly pitch left or right a bit. It would recover but that would put the machine left or right of its course. This was a bit problematic since I was tracking an actor running down a street. We finally got the shots we needed though. I noticed when spinning up the rotors that one was lagging behind the others. It looks like that motor was also along the axis of the shiver. With the machine sitting on the ground I turned each motor by hand to check their "feel". I discovered that the lagging motor turned with a noticeably more notchy feel than the other three. It isn't a bearing problem. It feels more like a magnet-to-rotor clearance issue. I checked the axial play to make sure a clip hadn't come off and there was none. The machine would still fly but it didn't fly happy. The bees didn't sound in sync if you know what I mean. Even though I'm flying with a GoPro, iOSD, and AVL58 the machines CG is well balanced. Anyway, I am offering the info to the collective in hopes that it will give you something to watch for with your machines. This kind of issue could be contributory to a fly-away (my opinion) if as is suspected that a sensor input overload can cause some kind of a software crash/corruption in the NAZA. On the plus side this was caught before it caused a crash or fly-away and B&H is replacing the craft for me. Kudos to B&H for great customer service.